Method for draw forming elongated shapes

ABSTRACT

A preformed elongated workpiece which has a hollow interior and an open side is placed in a machine with both exterior sides of the workpiece restrained. An arcuate forming tool is made having a length much shorter than the workpiece as, for example, about one-tenth as long. One end of the forming tool is given an exterior size and shape the same as desired at one end of the finished workpiece and the other end of the forming tool is given a size and shape the same as that desired at the opposite end of the finished workpiece. The forming tool is pivotally mounted on a carriage so that the large end of the forming tool is pressed into what will become the large end of the finished shape. The forming tool is then moved progressively from one end to the other of the workpiece and progressively rotated during its movement at a rate such that as the forming tool moves bodily from one end to the other of the workpiece, it is rotated progressively less rapidly in order to have the small end of the tool just reach a point of engagement with the workpiece when the carriage travel reaches the opposite end, thereby to proportionately change the size of the finished shape at a ratio of 10 to 1 as compared to the change in size of the forming tool. Rotation is accomplished by employment of a cam track on the machine and a cam follower connected to the pivotally moving forming tool. The workpiece is stretched endwise while the forming is being performed.

United States Patent lnventor [72] Wilford A. Swanson 10730 Wheatland, Sunland, Calif. 91040 [2!] Appl. No. 773,271 [22] Filed Nov. 4, I968 [45] Patented Aug. 3, 1971 [54] METHOD FOR DRAW FORMING ELONGATED SHAPES 4 Claims, 10 Drawing Figs.

[52] US. Cl 72/297, 72/150, 72/151, 72/319, 72/378 [51] lnt.Cl ..B2ldl1/02 [50] Field olSearch 72/151,

[56] Reierenes Cited UNITED STATES PATENTS 2,951,525 9/1960 Stamm 72/379 2.696.241 12/ 1954 Larsen 72/297 2,986,194 5/1961 De Marco... 72/297 2,872,964 2/1959 Hollis 72/297 2,880,780 4/1959 Mackey.'... 72/151 2,412,731 12/1946 Hoffman 72/151 Primary Examiner-Richard J. Herbst Assistant Examiner-Michael J. Keenan Altorney- Beehler & Arant ABSTRACT: A preformed elongated workpiece which has a hollow interior and an open side is placed in a machine with both exterior sides of the workpiece restrained. An arcuate forming tool is made having a length much shorter than the workpiece as, for example, about one-tenth as long. One end of the forming tool is given an exterior size and shape the same as desired at one end of the finished workpiece and the other end of the forming tool is given a size and shape the same as that desired at the opposite end of the finished workpiece. The forming tool is pivotally mounted on a carriage so that the large end of the forming tool is pressed into what will become the large end of the finished shape. The forming tool is then moved progressively from one end to the other of the workpiece and progressively rotated during its movement at a rate such that as the forming tool moves bodily from one end to the other of the workpiece, it is rotated progressively less rapidly in order to have the small end of the tool just reach a point of engagement with the workpiece when the carriage travel reaches the opposite end, thereby to proportionately change the size of the finished shape at a ratio of 10 to l as compared to the change in size of the forming tool. Rotation is accomplished by employment of a cam track on the machine and a cam follower connected to the pivotally moving forming tool. The workpiece is stretched endwise while the forming is being performed.

ATENTEDMJB 319m 3596"192 SHEET 1 0F 2 INVENTOR.

PATENTEDAUG 3m: 3595,4532

SHEET 2 BF 2 IQTTOQJEVS METHOD FOR DRAW FORMING ELONGATED SHAPES Certain types of draw forming and rolling metal sheets and related forms have been known and practiced for many decades. Most commonly, such methods and machines undertake to produce as an end result a sheet or other type form which is uniform in thickness from end to end. Where the form is a shape other than a flat piece as, for example, an angle, channel or l-l-shape, the aim is also to have the cross-sec tional configuration uniform from end to end. Such attempts as have been made to produce varied shapes and thicknesses have been particularly limited in application and versatility.

It is therefore among the objects of the invention to provide a new and improved method and machine for the draw forming of laterally open, hollow, elongated, preformed workpieces which is capable of giving to the workpiece any desired form from one end to the other and any desired thickness throughout the length which can be varied at will according to some preformed plan.

Another object of the invention is to provide a new and improved method for the draw forming of laterally open, hollow, elongated, preformed workpieces which makes use of a relatively small forming tool having a varied shape and size throughout its length and then applying it to the workpiece in such a manner that the position of the forming tool with respect to the work piece is varied progressively at a selected ratio so that the shape and thickness of the workpiece when made into a finished shape varies in a way corresponding to the forming tool but in a different ratio depending upon the ratio existing between the length of the workpiece and the length of the forming tool.

Still another object of the invention is to provide a new and improved method for draw forming laterally open, hollow, elongated, preformed workpieces wherein the attitude of a forming tool relative to the workpiece can be varied as desired, either by varying the shape of the forming tool or by varying the location of the workpiece-engaging portion of the forming tool relative to the workpiece whereby the finished shape can be given any desired form and thickness throughout its length, varying for example either from larger to smaller, from smaller to larger, or alternately varying between larger and smaller in virtually any desired sequence, while at the same time, ifneed be, varying also the thickness.

A further object of the invention is to provide a new and improved machine for the drawing of laterally open, hollow, elongated, preformed workpieces which is simple in its construction in that the workpiece is stationarily mounted and held in a working position, there being provided a forming tool, the workpiece-engaging surface of which can be varied to accommodate desired changes in the shape or thickness of the finished shape, the forming tool being pivotally mounted in engagement with an appropriate cam means capable of shifting the engagement of the forming tool with the workpiece from one point to another along the length of the forming tool and also shifting the approach of the forming tool to the workpiece so that by bringing it nearer the thickness can be reduced and by moving it further away the thickness can be increased at any desired point along the path of travel.

With these and other objects in view, the invention consists in the construction, arrangement, and combination of the various parts of the device, whereby the objects contemplated are attained, as hereinafter set forth, pointed outin the appended claims and illustrated in the accompanying drawings.

In the drawings:

FIG. I is a side perspective view of a laterally open, hollow, elongated, preformed workpiece.

FIG. 2 is a side view of the workpiece.

FIG. 3 is a side perspective view of an initial step in the construction of a forming tool.

FIG. 4 is a longitudinal cross-sectional view of the forming tool before being given its final shape.

FIG. 5 is a longitudinal sectional view of the forming tool after being curved to its final shape.

FIG. 6 is a cross-sectional view through the machine showing the forming tool in engagement with the workpiece when mounted on the machine.

FIG. 7 is a schematic plan view showing the forming tool in engagement with the workpiece at different stages of its progress from one end to the other.

FIG. 8 is a cross-sectional view on the line 8-8 of FIG. 7.

FIG. 9 is a cross-sectional view on the line 9-9 of FIG. 7.

FIG. 10 is a fragmentary cross-sectional view similar to FIG. 6 but showing a different way of mounting the workpiece in the machine.

In an embodiment of the invention chosen for the purpose of illustration certain elements of the machine which are productive of the desired results have: been shown in their mutual relationships while conventional portions of the machine have been merely suggested by way of environment.

A workpiece indicated generally by the reference character 10 has been shown in FIG. 1, which is elongated in character and has a hollow interior 11 and an opening 12 throughout the length of one side. The cross-sectional configuration is largely arbitrary and only roughly to size sufficient to permit it being placed in an appropriate female retaining form 13, as shown in FIG. 6. Although the specific length is not material to the machine and method, it may be assumed by way of example that the length C ofa finished shape 14 is 12 feet, and that the breadth A at the left hand as viewed in FIG. 2 is larger than the breadth B at the right end. A forming tool 15 is shown in FIG. 7 after its form has been completed and it has been properly mounted in the machine. To make the forming tool 15 there is provided a mold box 20 as shown in FIG. 3 having a mold cavity 21 therein which is onetenth the length C of the finished shape, the length of the mold cavity therefore in the chosen example being 24 inches. At a large end 22 of the mold cavity the cross-sectional shape is made the same as that desired of the large end 23 of the finished shape. The small end 24 of the mold cavity is made the same as the small end 25 of the finished shape. The cross-sectional shape of the interior of the cavity will therefore vary progressively from large to small throughout the length of the cavity.

Making use of the mold block 20 with its mold cavity 21 a metal or plastic form 25 is cast. As a consequence a large end 26 of the form 25 will have an exterior perimeter the same as that desired of the large end 23 of the shape and a small end will have its exterior perimeter the same as that desired for the small end of the finished shape 14, the length C being, in the chosen example, 24 inches.

The material of the form 25 should be such that it can be given a curved form such as that shown in FIG. 5 at which the material will take a permanent set whereby to produce the arcuate forming tool 15, as shown in FIG. 5. The large end 26' of the forming tool 15 will be the same shape and size as the large end 26 of the form 25 and the small end 27 will be the same shape and size as the small end 27 of the form 25, prior to bending.

Good practice suggests that the radius of curvature R be smaller than the radius of curvature R by an amount such that a concave side 29 be formed which coincides with a corresponding side of the small end 27. The radius of curvature R determines the radius of curvature of a convex side 30 which engages the workpiece. Where, for example, there is only a small amount of contact needed or where a small amount of contact could be tolerated because of close tolerances the radius R is small. Where the area of contact can be relatively larger as, for example, when drawing softer material, the radius of curvature R can be made correspondingly greater. The character of materials will dictate to a degree the radius of curvature, and also the prospect of galling the surface of the workpiece, which condition will be dependent to a degree upon the types of materials used respectively for the workpiece and the forming tool.

The machine is provided with a bed 35 stationarily mounted on some appropriate conventional support and a baseplate 36 of desired breadth and thickness ismounted upon the bed 35,

cavity 39, preferably machined to the shape, form, and size of the desired exterior of the finished shape 14. To further secure the female form box 37 in position in a manner preventing it from spreading during the draw-forming operation, use may be made of a hydraulic ram 40 suitably mounted on a conventional frame (not shown), a piston 41 of which engages a foot piece 42 at as many locations as may be desired throughout the length of the female form box to give it adequate support at all points.

For manipulating the forming tool 15 there is provided a carriage 45 which is mounted upon ascrew shaft 46 extending throughout the breadth of the machine as exemplified by the bed 35, the screw shaft being mounted upon conventional pillow blocks (not shown) and provided with a suitable conventional drive. An arm 47 is pivotally mounted on the carriage 45 by means of an appropriate pivot pin 48 as shown in FIGS. 6 and 7 bysome suitable meansas, for example, by employment of a tongue 49 on the arm and groove 50 the forming tool 15 may be appropriately secured to the am 47.

For rotating the arm 47 as desired, there is provided a cam follower in the form of a groovedwheel 51 rotatably mounted upon an extension 52 of the arm 47 so that the grooved wheel is in a position to follow along a cam track 53 embodied in a rod 54 which extends across the ,bed 35 of the machine. The slope of the rod and accordingly the cam track 53 is adjustable by means of adjusting screws 55 and 56 at opposite ends of the rod.

An additional element in the effective forming of the workpiece is to provide tension in a lengthwise direction on the workpiece while the interior surface is being formed.v To accomplish this a clamp 60 is applied to the workpiece at the right end as viewed in FIG. 2 and a similar clamp 61 at the left end. By appropriate conventional tensioning means a tensile stress sufficient to elongate the workpiece 2 or 3 percent is applied and continues throughout the operation.

In a second form of the device illustrated in FIG. a workpiece 65 is provided with flanges 66 and 67 running lengthwise along the side edges. The flange 67 overlies the baseplate 36 and the flange 66 overlies a leg 68 of an angle section, another leg 69 of which overlies the upper sidewall of the workpiece 65. Hydraulic rams indicated by the reference character 70 may be spaced longitudinally along the leg 69 and adjusted to a proper location to prevent expansion of the workpiece 65 while a forming tool 71, similai to the forming tool 15, is drawn through the forming operation.

In operation, after the forming tool has been constructed in substantially the manner hereinabove described, the workpiece 10 is placed in the female form box 37 and the box placed in the machine in the relative position shown in FIG. 6. The rams 40 are then manipulated to press down upon the upper side of the female form box to prevent the form box from spreading beyond a desired point. While the workpiece 10 is initially molded, it may be folded laterally slightly smaller than the elongated'cavity 39 or may be spread just slightly too wide to fit into the bottom of the cavity. This initial preforming or bending operation is not critical. Tension is then set up by manipulation of the clamps 60 and 61. The forming tool is moved by rotating the screw shaft 46 until the carriage 45 is at the left-hand end of the device as pictured in FIG. 7. At this point the left-hand end of the forming tool 15 projects into the hollow interior 11 of the workpiece 10 at its left-hand end, as viewed in FIG. 7. At the same time the grooved wheel 51 is riding on the cam track 53 at the high end which is adjacent the left side of the machine. The screw shaft 46 is then rotated by appropriate means and as a result of threaded engagement of the screw shaft with a threaded bore through the carriage 45, the carria e is adyanced progressivel along the screw shaft 46 from eft to right as viewed in F G57. t the same time the grooved wheel 51 roles along the cam track 53 and the convex side 30, which is the workpiece contacting side of the forming tool 15, engages frictionallywith the interior of the workpiece causing the arm 47 to rotate counterclockwise to an extent permitted by engagement of the groove wheel 51 with the cam track 53. Additionally, the thickness of the finished shape 14 is controlled by the radial distance between the point of rotation of the arm 47 and the point of engagement of the convex side 30 with the workpiece. For example, by having the radial distance from the center of rotation to the small end 27' greater than the distance between the point of rotation and the large end 26', the right end of the finished shape 14 will be thinner in gauge than the left end. Moreover, the thickness anywhere intermediate the ends of the finished shape can be controlled by controlling the radial distance between the center of rotation and the exterior of the convex side 30 at any selected point. Further still, variation in the form of the interior of the worksheet can be created by changing the character of the cam track 53 or of the grooved wheel 51 or some appropriately substituted cam follower. Other variations can be generated by changing the contour of the convex side 30. Although the machine and method is particularly applicable to the draw forming of material such as stainless steel, it can be used with comparable success on other metals capable of being formed by draw forming and other materials as well of such general character.

While the invention has herein been shown and described in what is conceived to be a practical and effective embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices.

I-Iaving described the invention, what I claim as new in support of Letters Patent is:

1. A method for changing a laterally open, hollow, elongated, preformed workpiece into a finished shape having a selected length and respective large and small ends comprising preparing a forming tool having a length which is a relatively small fraction of said selected length of the workpiece, and giving to one end of the forming tool a relatively larger exterior shape corresponding to the large end of said finished shape and the other end a relatively smaller exterior shape corresponding to the small end of the finished shape forming the exterior of said forming tool throughout its length in a longitudinally arcuate configuration,

supporting opposite sides of the workpiece throughout the length thereof against a laterally spreading displacement, pressing one end of said forming tool into engagement with one end of said workpiece, then drawing the workpiece to finished shape by moving said forming tool from said one end of the workpiece to the other end of the workpiece and simultaneously rotating said forming tool as the tool is moved from said one end to the other at a progressive rate such that when the tool reaches said other end of the workpiece the other end of the tool will be in engagement with the other end of the workpiece, proportionately to the shape of said forming tool.

2. The method as in claim 1 including stressing said workpiece in a lengthwise direction while said forming tool is being pressed into engagement from end to end of said workpiece.

3. The method as in claim 1 including supporting said workpiece on the side opposite the side being formed.

4. The method as in claim 1 including varying the thickness of the workpiece while varying the cross-sectional shape of the inside thereof. 

1. A method for changing a laterally open, hollow, elongated, preformed workpiece into a finished shape having a selected length and respective large and small ends comprising preparing a forming tool having a length which is a relatively small fraction of said selected length of the workpiece, and giving to one end of the forming tool a relatively larger exterior shape corresponding to the large end of said finished shape and the other end a relatively smaller exterior shape corresponding to the small end of the finished shape forming the exterior of said forming tool throughout its length in a longitudinally arcuate configuration, supporting opposite sides of the workpiece throughout the length thereof against a laterally spreading displacement, pressing one end of said forming tool into engagement with one end of said workpiece, then drawing the workpiece to finished shape by moving said forming tool from said one end of the workpiece to the other end of the workpiece and simultaneously rotating said forming tool as the tool is moved from said one end to the other at a progressive rate such that when the tool reaches said other end of the workpiece the other end of the tool will be in engagement with the other end of the workpiece, proportionately to the shape of said forming tool.
 2. The method as in claim 1 including stressing said workpiece in a lengthwise direction while said forming tool is being pressed into engagement from end to end of said workpiece.
 3. The method as in claim 1 including supporting said workpiece on the side opposite the side being formed.
 4. The method as in claim 1 including varying the thickness of the workpiece while varying the cross-sectional shape of the inside thereof. 